Moody’s also raised the baseline credit assessment (BCA) for these three banks from b2 to b1.

ACB's problem loans ratio, as adjusted by Moody's, declined to 0.95% at the end of 2017 from 2.99% at the end of 2016, driven largely by the full write-down of the VND1.5 trillion (US$66 million) of bonds issued by the Vietnam Asset Management Company (VAMC), it added.

Similarly, MBBank’s problem loans ratio fell from 4.7% in 2016 to 2.9% in 2017 mainly due to the full write-off of VAMC bonds for VND3.4 trillion (US$149.6 million).

Moody's expects ACB and MBBank's asset quality to remain stable over the next 12-18 months on the back of an improvement in the operating environment, which will in turn support the repayment capacity of the bank's borrowers.

As for Techcombank, its BCA upgrade is driven by improved solvency metrics, namely capital, asset quality and profitability.

Moody's estimates that the bank's tangible common equity to risk-weighted assets increased to 14.5%, from 9% in 2016, giving Techcombank the largest core capital buffer among the 16 Moody's-rated banks in Vietnam.

At the same time, Moody's has affirmed the long-term local- and foreign-currency deposit and issuer ratings of Vietnam Prosperity Joint Stock Commercial Bank (VPBank) at B2, and upgraded the bank's BCA to b2 from b3.

The upgrade of VPBank's BCA takes into account the bank's high profitability, as well as its improved capital buffer. The BCA also considers VPBank's heightened credit risks from its consumer finance portfolio, and weak problem loan coverage compared to domestic and global peers.